Currently btrfs uses libblkid to scan for block devices with BTRFS.
The disadvantage is that this method is expensive. The udevd maintains
information about all block devices in udev db and all devices are
probed by udevd (it's linked with libblkid). We don't have to duplicate
this thing in btrfs.
This patch links btrfs with libudev, the original blkid based method
is used as fallback (for systems without udev, etc.)
Note that btrfs-progs project does not use autoconf, so dependence on
libudev is hardcoded to Makefile for now. It would be probably better
to add ./configure script to the project and make dependence on
libudev optional.
udev:
# time ./btrfs device scan
Scanning for Btrfs filesystems
real 0m0.012s
user 0m0.004s
sys 0m0.003s
blkid:
# time ./btrfs device scan
Scanning for Btrfs filesystems
real 0m0.076s
user 0m0.008s
sys 0m0.024s
Signed-off-by: Karel Zak <kzak@xxxxxxxxxx>
---
Makefile | 2 +-
utils.c | 107 +++++++++++++++++++++++++++++++++++++++++++++++++--------------
2 files changed, 84 insertions(+), 25 deletions(-)
diff --git a/Makefile b/Makefile
index 203597c..768c5e0 100644
--- a/Makefile
+++ b/Makefile
@@ -26,7 +26,7 @@ TESTS = fsck-tests.sh convert-tests.sh
INSTALL = install
prefix ?= /usr/local
bindir = $(prefix)/bin
-lib_LIBS = -luuid -lblkid -lm -lz -llzo2 -L.
+lib_LIBS = -ludev -luuid -lblkid -lm -lz -llzo2 -L.
libdir ?= $(prefix)/lib
incdir = $(prefix)/include/btrfs
LIBS = $(lib_LIBS) $(libs_static)
diff --git a/utils.c b/utils.c
index cc33cfc..5c71336 100644
--- a/utils.c
+++ b/utils.c
@@ -38,6 +38,7 @@
#include <linux/kdev_t.h>
#include <limits.h>
#include <blkid/blkid.h>
+#include <libudev.h>
#include "kerncompat.h"
#include "radix-tree.h"
#include "ctree.h"
@@ -2181,20 +2182,34 @@ int test_dev_for_mkfs(char *file, int force_overwrite, char *estr)
return 0;
}
-int btrfs_scan_devices()
+static int scan_device(const char *path)
+{
+ int rc;
+ int fd = open(path, O_RDONLY);
+ struct btrfs_fs_devices *devs = NULL;
+ u64 ndevs;
+
+ if (fd < 0) {
+ printf("ERROR: could not open %s\n", path);
+ return 1;
+ }
+
+ rc = btrfs_scan_one_device(fd, path, &devs, &ndevs, BTRFS_SUPER_INFO_OFFSET, 0);
+ if (rc)
+ printf("ERROR: could not scan %s\n", path);
+
+ close(fd);
+ return rc;
+}
+
+
+static int btrfs_scan_devices_by_blkid(void)
{
- int fd = -1;
- int ret;
- u64 num_devices;
- struct btrfs_fs_devices *tmp_devices;
blkid_dev_iterate iter = NULL;
blkid_dev dev = NULL;
blkid_cache cache = NULL;
char path[PATH_MAX];
- if (btrfs_scan_done)
- return 0;
-
if (blkid_get_cache(&cache, 0) < 0) {
printf("ERROR: lblkid cache get failed\n");
return 1;
@@ -2209,29 +2224,73 @@ int btrfs_scan_devices()
/* if we are here its definitely a btrfs disk*/
strncpy(path, blkid_dev_devname(dev), PATH_MAX);
- fd = open(path, O_RDONLY);
- if (fd < 0) {
- printf("ERROR: could not open %s\n", path);
- continue;
- }
- ret = btrfs_scan_one_device(fd, path, &tmp_devices,
- &num_devices, BTRFS_SUPER_INFO_OFFSET, 0);
- if (ret) {
- printf("ERROR: could not scan %s\n", path);
- close (fd);
- continue;
- }
-
- close(fd);
+ scan_device(path);
}
blkid_dev_iterate_end(iter);
blkid_put_cache(cache);
- btrfs_scan_done = 1;
-
return 0;
}
+static int btrfs_scan_devices_by_udev(void)
+{
+ int rc = 1;
+ struct udev *udev = NULL;
+ struct udev_enumerate *en = NULL;
+ struct udev_list_entry *ent, *devs;
+
+ udev = udev_new();
+ if (!udev)
+ goto done;
+ en = udev_enumerate_new(udev);
+ if (!en)
+ goto done;
+
+ udev_enumerate_add_match_subsystem(en, "block");
+ if (udev_enumerate_scan_devices(en) != 0)
+ goto done;
+ devs = udev_enumerate_get_list_entry(en);
+ if (!devs)
+ goto done;
+
+ udev_list_entry_foreach(ent, devs) {
+ const char *val, *name = udev_list_entry_get_name(ent);
+ struct udev_device *dev = udev_device_new_from_syspath(udev, name);
+
+ if (!dev)
+ continue;
+ val = udev_device_get_property_value(dev, "ID_FS_TYPE");
+ if (val && strcmp(val, "btrfs") == 0) {
+ const char *path = udev_device_get_devnode(dev);
+ if (path)
+ scan_device(path);
+ }
+ udev_device_unref(dev);
+ }
+
+ rc = 0;
+done:
+ udev_enumerate_unref(en);
+ udev_unref(udev);
+
+ return rc;
+}
+
+int btrfs_scan_devices()
+{
+ int rc = 1;
+
+ if (btrfs_scan_done)
+ return 0;
+
+ rc = btrfs_scan_devices_by_udev();
+ if (rc)
+ rc = btrfs_scan_devices_by_blkid();
+
+ btrfs_scan_done = 1;
+ return rc;
+}
+
int is_vol_small(char *file)
{
int fd = -1;
--
1.9.3
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